Mechanism for the interconversion of reciprocating and rotary motion



v Se a t 4, 1928.

. 1,682,924 A. G. M. MICHELL MECHANISM FOR THE INTERCONVERSION OF RECIPROCATING AND ROTARY MOTION Filed Jan. 26, 1927 40 which and the front end the P P. 45 yoke, wh1ch 1s a portion of a cyhnder coaxial I Patented Sept. 4,1928;

ANTHONY GEORGE MALDON IIOH EIJQ'OI' ESPATENT OFFICE.

mnounnn, vicious, nus'rnnnn, as

sisnoa 'ro omxnnss nemnsnmmnn or museum, nnsrmm."

- .np ucanonaiea miser e,'19=1','am1 Io.

Thepresent invention relates ,to improvements in mechanisms. for the interconversion of rotary'and reciprocating motion of the class comprising the combination of-a rotating swash plate 'or slant with one or. more reciprocating elements or pistons to each ofwhich is rigidly attached-a. oke member partially embracin'g'the periphery of the'rotating slant and carrying a pair of pivoted 'sli m pers which make sliding contact with e 7 plane faces oftheslant. 4

The primary objects of the present invention are the attainment of eater strength and rigidity in the yoke memfir, and the proin vision upon it of a film-lubricated surface by.

which-it is supported upon the periphery. of the slant with a sliding contact involving a minimum of-fricti on. 5 v

Accordin' to theinvention, the yoke-mema0 ber is rigi y connected to the outer or front end of the reciprocating element or piston and is of a crescent-shaped section, referably hollow, having inner and outer cyindrical bearing. surfaces of which thelatter slides '25 lon 'tudinally. in a stationary part of the i mec anism, while the 'former is in contact with the periphery of'the slant as above stated. The yoke carries, rigidly attached to or formed upon its outer end a lugbetween iston are mounted by means of ball-joints articulations, in suitably-shaped pivoted seatings, a pair of slippers arranged one on either side of p the slant and having plane working 'faces making lubricated contact with the plane faces of the slant, the centres of the-ball joints being eccentri'c'to the axis ofthe outer cylindrical bearing surface of the yoke.

' The construction of the yoke may be varied according as thereciprocating element-actuates-the slant or vice versa. Bothin the former class of machine, for brevity called a motor, and in thelatter. class, called'a' the external bearing surface of the.

with the piston, fits a corresponding 0 lin drical surface bored in a fix'ed'part o the mechanism. v

In the accompanying drawings" Figure -.1

go'is a longitudinal section of a reciprocating -element, together with parts co-acting with such element, according to the invention.

Figure 2 is a cross section on line II-II of Figure 1 of the yoke-portion of the reci re- .55 eating element. its-preferably construe 1n 7, 8 and cups 4",.5 on a line P-P para el to,

'168,765, and 1n amt mean 4 m 7, me

the case of a motor. Figure 3 is a similar v1ew of the preferred construction for the case of a pump, and Figure 4 is a longitudinal section similar to Figure 1 of the yoke-portion of a reciprocating element according to an alternative mode of construction;

In -so far as shown by Figures 1 and 4, the constructions for a pump and for'. a motor arealike. As shown in Figure I the reciprocating element consists of a piston 1, of usual construction arranged to reciprocate in a cylinder whose axis. is the line C- -O, and of a yoke-2 having at its outer end an integral lug 8 and 4 carrying slippe 4, 5,which are pivoted inlpp rbups 4, 5'1 by means. ofhemispherical ball pivots 7 an 8,'these slippers'making lubricated contact withthe-slant 6 which revolves about the axis 0-0. Each of these parts except the yoke is of known construction. Y

As re ards the eiieral form-of the slant,

piston element an slippers, reference maye made to United States PatentBe-issue No." 15,756, whilst in United States Patent .No. 1,603 852, a yoke construction is described resembling that of the present case in so far as its outer cylindrical bearing surface is de scribed. In that case however, as in all; other descriptions of mechanisms of this class hith-- e'rto published, the said outer bearing surface was concentric with theball-pivots of the slippers and the yoke had no contact with the outer peripher of the slant' In addition to t e formation of the yoke. section of segmental section with inner and outer bearing surfaces as above described,-

a feature of the present invention is the location of the common axis of the ballivots v but eccentric with respect to, the axis C-C of the outer cylindrical surface of the yoke and liying" between that axis and the ax1s'OO.

'he importance of this last feature will be seen from the explanations hereinafter given.

' Theyoke 2,

motor asshown in cross-section i-n' Fi re 2,

is of". a hollow crescent-shaped form, its internal surface-11, which is a portion of a cylindrical surface coaxial with the slant 6, 1m fitting the external periphery of the latter.

The external surface 9ofithe yoke is also cylindrical ,and is asliding fit in a corresponding cylindrical guide surface 10, formed in a stationary part of the mechanism, with the adapted for application m a same or nearly the same axis C-C as the motor cylinder. In the construction of the yoke,

,2, adapted tothe case of apump as shown in Figure 3, the internal wall of the yoke in- 1 stead of being of a plain crescent section, as

in Figure 2, is formed with a lateral wing 12 on the leading side of the yoke to provide an extension of the surface 11 which bears on the periphery of the slant 6 in the direction opposite to the direction of rotation which is shown by the arrow A. 'A- correspondin lateral portion of the internal surface 11, 1s removed from the side opposite to the'projecting wing 12, a shallow recess being thus formed as shown at 13.

It will be understood that with each of these constructions, the lateral components of the working pressures on the slippers at the beginning and end of the working strokes slipper ball 8 onthe oke in te tangential direction op osite to t c direction ofImotion of the. slant indicated by the arrow A, is e'quilibrated b \the resultant of a force (referred to and in icat'ed'by the symbol R) which is: exerted radially outwards by the periphery of the slant on the internal surface 11' of the yoke, and of a force (referred to and indicated by the symbol S) exerted radially inwards -upon the outer cylindrical surface 9 of'the yoke by the guide surface 10. The lines of action of the reaction T and forces R and S intersect at a point which is at the rear of the pivot of the sli per 5. j

In the case a pump, as shown in Figure 3, in which the forces, pressures and direction I of motion are represented by responding to those of Figure 2, the lateral symbols corcomponent of pressure '1, exerted by the slip er on the yoke at the middle of the wor 'ng stroke acts in the direction A of the motion of the slant, and the forces R and S exerted 'on the yoke by the slant and guide surface 10 res ectively act in directions as shown in the v gure. The point of intersection of the lines of action of T, R and S in this case intersect at a point in front of the pivot 8 of the slipper 5. .The win 12, and recess 13 are however constructe of such ure 3 the po1nt ofaction of the bearing force upon the internal bearing surface 11 and the slant.

of the yoke is towards the rear or leading end of that surface havin regard to the direction of rotation of the slant. Wedge-film lubrication is thereby rendered possible, the centre of the fluid pressures in the film of lubricant between the surface 11 and the eriphery of the slant coinciding with the po1nt of'action of the force R,

The construction and functions of the yoke shown in Figure 4, are the same as those described in connection with Figure l and eitherFigure 2 or Figure 3, except that the outer lug 3, instead'of being integral with the yoke 2, is rigidly attached theretd by one or more bolts 14, whichpreferably passes .or pass through the hollow. crescental portion of the yokehsshown. By this construction the assembly is facilitated of the cups 4 and 5* and slippers 4 and 5 in relation to the yoke 2,3.and the slant'6. By this means furthermore the different thermal expansibility of suitable materials such as steel in the bolt or bolts 14, and aluminium alloy in the yoke 2, may .be utilized to prevent undesirable changes, due to variations of temperature, in the distance between the centres 'of the ball pivots 7 and 8, and consequent variations of the working clearances between the slippers In certain cases,'as'for. instance when the metal of which the yoke is construbted is unsuitable for service as a bearing material, one

'or both of the bearing surfaces. 9, 11 instead .of being formed directl upon the yoke, may bepipon separate mem ers rigidly or nonrigi yattachedthereto thesemembers when non-rigid being preferab pers plvoted at points corres onding to the ints of intersection of the ines of action and R with the surfaces 9 and 11 respectively. 'Alternatively' in the case of the exernal surface of the yoke, a special bearing member may be provided to suppl the external bearing surface 10 this mem r being either rigidly or non-rigidl and in the latter case preferably stationary part c 1. In mechanism-for the interconversion of reciprocating and rotary motion in combinathe mec anism.

ly arranged as slippivotally attached to the tion, a reciprocating member, a swash plate, a

yoke member-connected to said reciprocating member, slipper members pivotally carried by the reciprocating member and the yoke member an engagingwith o posite sides of the swash plate, an outer cy mdrical guide surface on said yoke eccentric to the pivots of yoke member connected to the reciprocating member, a pair of pivoted slipper members, means on the outer end of the reciprocating member carrying one of said slipper members, a lug on the outer end of the yoke membercarryin'g the other of said slipper members, said slipper members engaging with opposite sides of the swash plate, an outer cylindrical guide surface on said yoke, eccentric to the pivots of said slipper members, a stationary member engaging said outer cylin drical guide surface, and an inner cylindrical guide surface on said yoke parallel to and in sliding contact with the periphery of the swash plate. 1 a

3. In mechanism for the interconversion of reciprocating and rotary motion in combination, a reciprocating member, a swash plate, a yoke member connected to said reciprocating member, pivoted slipper members carried .by the reciprocating member and the yoke member and engaging with opposite sides of the swash plate, an outer cylindrical guide surface on said yoke eccentric to the pivots of said slipper members, a stationary element engagin said outer cylindrical surface, an inner cy indrical guide surface with a wing projecting" on the leading side of said yoke with said inner cylindrical guide surface and its wing parallel to and in sliding contact with the periphery of the swash plate.

4. In mechanism for the interconversion of reciprocating and rotary motion, in combination, a reciprocating member, a swash plate,

' a yoke member connected to the reciprocating member, a pair of pivoted slipper members, means on the outer end of the reciprocating member carrying one of said slipper members, a separate lug member attached to the outer end. of the yoke member carr ing the other of saidslipper members, sai slipper members engaging with opposite sides of the swash plate an outer cylindrical guide surface on said yoke, eccentric to the pivots of said slipper members, a stationary member engaging said outer cylindrical guide surfacg, and an inner cylindrlcal guide surface on said yoke parallel to and in sliding contact with the periphery of the swash plate.

5. In mechanism for the interconversion of reciprocating and rotary motion, in combination, a reciprocating member, a swash plate,

a yoke member connected to the reciprocating member, a pair of pivoted slipper members, means on the outer end of the reciprocating member carrying one of said slipper members, a separate lug member attached to the outer end of the yoke member carrying the other of said slipper members, means fasten:-

ing said lug to the yoke member having a coefficient of-therma1 expansion different from that of the yoke member, said sli per members engaging with opposite si es of the swash plate, an outer cylindrical guide surface on said yoke eccentric to the pivots of said slipper members, a stationary member ciprocable device having an axis more remote from the axis of the swash plate than are the pivots of the slipper members, a stationary element in sliding engagement with said guide surface, and .an inner cylindrical guide surface on said reciprocable device over the swash plate and concentric with the periphery thereof. 7

Dated this 24th day of December 1926.

ANTHONY GEORGE MALDON MICHELL, 

